Tube coupling



March s;1949. A, E, EY 2,463,883

TUBE COUPLING Filed April 24, 1946 Ja a :7

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Patented Mar. 8, 1949 UNITED STATES PATENT OFFICE TUBE COUPLING Alvin E. Kinsey, Chattanooga, Tenn., assignor to Furlow-Cate Manufacturing Company, Inc., Hapeville, Ga., a corporation of Tennessee Application April 24, 1946, Serial No. 664,590

2 Claims. 1

This invention relates to tube coupling and aims generally to improve the same. The invention is particularly adapted for forming a perfect fiuidtight seal that may be broken and replaced at will for handling high or low pressure gas, air, or other fluid, and is especially applicable to forming such connections in lines of soft metal tubing such as copper, aluminum and the like.

A primary object of the invention resides in the provision of a coupling of the class described having a minimum number of parts and assuring a pressuretight seal.

A further object resides in the provision of a coupling in which all parts are self aligning insuring a true and accurate fit.

A further object resides in the provision of cooperating abutments adapted to afford a multiple seal of the coupling against leakage and to provide, by employing the ductility of the tubing itself, a pressure packed connection which may be broken and reassembled without excessive care, and yield again a fully pressuretight joint.

Further objects and advantages of the invention, as will appear from the following description of preferred embodiments thereof, reside in the provision of an improved method of coupling and improved features and combinations of parts contributing to the realization of the aforesaid objects.

In the accompanying drawings of preferred embodiments illustrative of the invention Fig. 1 is a longitudinal sectional view of one form of coupling prior to tightening of the same.

Fig. 2 is a similar view of a second form showing the parts in tightened relation.

Figs. 3 and 4 are enlarged fragmentary sections showing the relation of the parts prior to and following effecting of the seal, being made somewhat diagrammatic and exaggerated in the interest of clarity.

Referring to the drawings of the illustrative embodiments in which like reference numerals indicate like parts, the tube II] to be connected is preferably a soft metal tube of aluminum or copper, for example, and is provided with a squared end I I at its extremity which in the form shown is slightly internally beveled, as at Ila (see Figs. 1 and 3) At a predetermined distance from the tube end ll, preferably a distance greater than the radius but less than the diameter of the tube, the tube I'll is provided with an integral outwardly struck annular boss or bead I2 preferably hollow and of the rounded V-shape shown, and preferably having its side walls l3 and I4 (Figs. 1 and 3) inclined at substantially 45 relative to the axis of the tube for the purpose hereinafter described.

The coupling further comprises the body member I5 having a cylindrical bore I6 of a substantially smaller diameter than the external diameter of tube It! and preferably corresponding in diameter to the internal diameter of the tube as shown. The body member I5 is further provided with a cylindrical counterbore l"l concentric with the bore l6 and of a diameter to closely but freely receive the end of the tube Il'l (see Fig. 3) and with an outwardly flared shoulder [8 at the outer end of the counterbore I! to be engaged by the adjacent wall l3 of the V-shaped hollow boss if when the coupling is assembled. At the junction between the bore l6 and counterbore I1 the body member is provided with an annular seat, preferably undercut on a reverse bevel as shown, which desirably has an angle of about 30 providing a pocket between the seat l9 and the adjacent wall of counterbore l'l. As best shown in Figs. 3 and 4 counterbore H has a deptlr slightly less than the predetermined length of the portion of the tube Ill between the tube end H and boss l2 so that on assembly of the fitting the tube end I I' engages with the annular seat I 9 prior to the engagement of wall l3 with shoulder I8. In other words, the spacing of the outer and inner abutments l 8 and I9 of the counterbore must be so related to the spacing of the beveled abutting faces Ila and I3 of the tube, that when the coupling is tightened, the face I la will be forced into pressure-tight engagement with the face I'9 before the engagement between faces l3 and I8 arrests such forcing movement. In the ideal case, with face I9 undercut at the same angle as countersunk-face Ila, the spacing between faces II and I3 might be just enough greater than that between faces l8 and I9 to correspond to the depth of the bevel Ila, so that the bevel lla would engage substantially simultaneously with the first contact at l8 and be forced into sealing relation during the slight movement of the tube relative to face I8 that accompanies tightening of the coupling. However, as the depth and angularity of the bevel Il'a and the face I9 may vary, and as the angle of the bevel Ila, being made with a different tool, may differ slightly from that of I9 (as illustrated to an exaggerated scale in Fig. 3), it is preferred to have the excess, of the spacing of faces I I and l 3 over that of faces l8 and I'll, slightly greater than that which would be required in the ideal case. The departure from the ideal in this con nection in the case of a hard drawn or heavy tube 3 would, of course, be less than in the case of a very soft one.

The body member I further comprises a suitable connecting element 2d of any desired form. In the form shown in Fig. 1, this element comprises an internally pipe threaded head 26a. externally formed at of hexagonal or other shape or otherwise arranged to enable the body member I5 to be engaged with a pipe member or be securely held during assambly of the coupling. In the form shown in Fig. 2 the element 2|] comprises an externally machine screw threaded nipple 20c and a hexagonal or other holding or turning element d, exemplifying other arrangements which may be adapted for associating the coupling of this invention with other structure.

The third member of the tube connector, as is best shown in Figs. 1 and 2, comprises a coupling element 25 which is slipped over the tube Ill before formation of the boss I2 therein, but which may be assembled on the tube from its other end before distortion thereof. This coupling 25, which is further detailed in Figs. 3 and l, is annular in form and is provided with an annular shoulder 26 formed to engage against wall ill of boss I2 in the assembly of the tube connection. Shoulders I8 and 25 of the body and coupling elements I5 and 25 are preferably formed at an angle of approximately 45 as hereinafter described, and side walls I3 and I l of boss I52 are desirably given a corresponding inclination.

Suitable means is provided for associating the couplin element 25 with the body element I5, in the forms shown by the provision of a threaded engagement between these members. In the illustrative embodiment the coupling element 25 which is slipped over the tube it? embraces the tube loosely at is shouldered end 26 remote from the body member I5 and has a female threaded portion 21 which lies in spaced relation to the tube at a distance sufficient to accommodate boss I2, and which engages with a male threaded connection 28 formed externally of body member I5, beyond the smooth lead-in or guide portion 29.

With the construction described, the coupling element 25 having first/been slipped over the end of tube I0, the tube, provided with the squared end I I, is upset to form boss I2,preferably by at least externally supporting the tube wall at each side of the area to be upset and applying longitudinal pressure to the squared end II. This operation results in slightly thickening the metal of the tube wall throughout at least the area distorted to form boss I2, and this operation is preferably performed with external support of the tube only so as to thicken the metal wall slightly in the portions of tube Ill adjacent to the boss without enlargement of their external diameter, thus increasing the strength of the tube at these areas for the purpose hereinafter described. The boss I2 having been upset the tube end II is slipped into the counterbore I! of body member I5, in which it has an easy slidin fit, and its end II comes to rest against the seat I9, with boss wall I3 still in slightly spaced relation to shoulder I8 as shown to an exaggerated scale in Figs. 1 and 3. The coupling element 25, guided and aligned by tube I0 is slipped over the unthreaded end 29 of the body member I5 which serves as a further guide to align the threaded section 2'! of the coupling member 25 with the threaded section 28 of body l5. The threaded sections 21 and 28 engage with one another and preferably are screwed together throughout all but a few turns of their interlocking engagement before the shoulder 26 abuts wall I4 of boss I2. Further tightening of the couplin element thereafter forces the tube end II into tight engagement with seat I9 and compresses the tube end against the seat to such extent that the relatively soft metal of the tube is caused to flow and come to a pressure tight engagement with the annular seat I9 as exempliiied by area a, Fig. 4.

In the preferred embodiment in which the annular seat is reversely undercut on an angle of about 30 as shown, the compression of the tube end face I'IIIa on the inclined surface I9 causes a further flow of metal forcing an annular section of the tube closely adjacent to the tube end II to expand into pressure tight engagement with the wall of counterbore I'I, adjacent the annular seat I9, as exemplified by area b, Fig. 4. This same tightening operation of the coupling element 25 causes the coupling shoulder 26 to press against wall I4 of boss I2 and moves the tube until wall I3 of the boss engages shoulder I8, thereafter compressing boss I2 between the shoulders I8 and 26 as shown in Fig. l. By this means a multiple fluidtight seal is effected, the first seal lying in the area exemplified at a, Fig. 4 constituting the primary seal, the further seal lying in the area exemplified at b, in the preferred embodiment constituting an added primary seal, the additional seal effected. in the area of engagement between shoulder I8 and boss wall I3 constituting a secondary seal, and some additional sea-l also being effected by the engagement of walls HI and 2.6 and the threaded engagement between parts 27 and 28, Figs. 1 and 2. As the primary seal or seals are made at protected regions, any denting or other minor damage of the end I8 of body I5, even if it extends into the flared shoulder I8 itself, is rendered inconsequential so far as the primary seal is concerned.

As is further apparent from Fig. 4,the particular manner of coupling by means of seat I9 engaging tube end II and the gripping of tapered boss 12 between shoulders I8 and 26 itself may effect a slight thickening of the tube Ill adjacent the end II, thus further insuring against thinning of the tube, throughout the extent of the coupling. As before mentioned, the mode of upsetting the boss I2 as shown in Figs. 3 and 4 has itself preferably produced a slight thickening of the tube wall in the area including'th'e boss and this construction thus increases the strength of the tube at the coupling compared with its strength throughout the balanceof the line. -By virtue of this improvement, fracture of the tube within the coupling is obviated and no thinning or weakening of the tube occurs as is experienced in the flanged-end type of coupling, nor does any thinning of the tube Wall-accompanytightening of the coupling, as occurs when separate ferrules are employed designed to compress into, bite into, the metal of an initially straight tube wall. Further 'by limiting the depth of the counterbore H, as described, provision is made for radial support of the tube end II against inward bending by its engagement with the seat I9, and as this support is afforded in relatively close relation to the boss I2 no material inward jamming of the tube wall occurs which would restrict the passage of the coupling nor is there any tendency towards tearing of the tube wall. In addition by the rounded V-shaped construction of boss I 2 filleted corners are provided avoiding presence of any sharp angles at which stresses could concentrate and lead to metal fatigue in the event of long continued vibration in the line. Most importantly, by this construction the tube is gripped and supported at the boss area I4 which is separate and spaced from the primary sealing surfaces at and b Fig. 4 so that stresses applied to the tube are in no instance transferred to the primary sealing surface to cause loosening thereof.

As above mentioned, a particularly advantageous embodiment of this invention contemplates a reverse bevel of the seat I9 and about 45 bevels of the surfaces l8 and 26 with substantially similar inclinations of walls I3 and I4 of boss I2. Further, the preferred embodiment of the invention employs a boss struck out of the metal of the tube by an amount approximately equal to or somewhat greater than the thickness of the tube wall, thus providing a somewhat flexible but substantially continuous metal area in most of that portion of boss l2 lying between the clamping shoulders I8 and 26. Due to the difference in taper between the shoulder 26 and the seat I9, the frictional contact of shoulder 26 against wall M is relatively great and tends to sweat the tube end II into firm engagement at the areas a and b in the preferred embodiment, while the near continuity of metal in the boss tends to avoid undue flattening of the boss and to cause instead a slight camming action of shoulders l8 and 26 against the boss forcing it into a condition of radial as well as longitudinal compression. As will be apparent, the creation of radial compression in the areas of the tube comprising and adjacent to boss I2 afiords further strength and loffsets any tension stresses transferred from the tube line.

Further, since as shown in Fig. 4, the entire end of tube I9, between the tube-end II and the boss I 2, bridges between the primary sealing areas a and b and the integral boss I2, access of pressure from the line to the space between this bridging portion and the counterbore wall I! is prevented. Thus in very high pressure lines, the pressure tends solely to straighten the bridging portion outwardly against the bore wall l1, and by this straightening tendency tends to force the tube end I I still more firmly into pressure sealing relation to the primary sealing areas a and b.

On unscrewing of the coupling element 25 to effect release of the connection the frictional contact between more steeply inclined surfaces l4- and 26 is sufiicient so that, in conjunction with the slight resiliency of the metal of the tube end II, it effects a loosening of the tube from seat I9, obviating any necessity for gripping and distorting the tube I0 in effecting its withdrawal from the body member,

After the coupling has once been drawn to a pressure tight joint and thereafter released it is found that the metal adjacent to the tube end in the area exemplified at b (Fig. 4) has been expanded into snug sliding fit with the counterbore I7, and that the annular area of contact exemplified at c, Fig. 4, is of considerable extent, and not as concentrated as that at d, Fig. 4. Since the counterbore I1 is preferably machined to a smooth cylindrical surface the expanded tube end Il may nevertheless be readily pulled out of the counterbore and can be readily reinserted, the beveled shoulder l8 acting as an entrance guide for this purpose. On re-insertion it is not necessary to make certain that the tube It] takes the same rotative position relative to seat I9 that it had on first assembly, since by re-tightening the coupling member 25 to an extent somewhat greater than that effecting the original seal, a further compression is applied to the boss producing a further flow of metal at the tube end and again affording a pressure tight primary seal.

By the construction of the boss and the initial relatively free fit of the parts, provision is made for a camming inwardly of boss l2 by shoulder I8 on tightening of the connection, thus producing a slight arching and longitudinal movement of tube I0 relative to body member I5, and introducing slight additional tube length inside the counterbore I! to insure full compression against the annular seat even after numerous re-sealings of the joint. The modes of contact achieved at the area exemplified by c and d in Fig. 4 also tend; to insure longitudinal camming of the tube end, if necessary, to obtain a tight seal. It will further be apparent that the present construction is of great simplicity employing only two members in addition to the tube itself, that the sliding engagement of the parts provided is of a nature to make all members self-aligning and self-centering, and that accordingly no difficulty with crossed threads is encountered, nor is any jamming of the tube ends experienced.

As used herein the term squared end, or squared end face, has reference to the fact that the end ll of tube I0 is cut on a plane normal to the axis of the tube, regardless of whether the tube end is planar before the coupling is tightened, or whether it is somewhat pre-beveled or countersunk as at Ila, toward the shape assumed by it in Fig. 4, as is usually desirable in the practice of this invention.

From the foregoing description it will be apparent that the embodiments shown and described are but illustrative and not restrictive of the invention herein described and claimed and that inventive features and combinations of this disclosure may be embodied in other specific forms.

What is claimed is:

1. A tube coupling comprising a cylindrical tube, said tube having a squared end face and an integral outwardly struck rounded V-shaped boss spaced a predetermined distance from said end face, a body member having a cylindrical bore of a substantially less diameter than the external diameter of the tube and having a cylindrical counterbore concentric therewith of a diameter to closely but freely receive the tube end, said body having an outwardly flared shoulder at the outer end of the counterbore to be engaged by the adjacent wall of said V-shaped hollow boss and said body having an annular seat at the juncture of said bore and counterbore to be engaged by the squared end face of said tube, said shoulder and seat being spaced from one another by a distance slightly less than the predetermined spacing of said boss and tube end face so that said tube end face engages with said annular seat prior to the engagement of said boss with said shoulder, and a coupling element embracing said tube and threadedly engaging with said body member, said coupling element having a flared shoulder for engaging the other wall of said boss, whereby on insertion of said tube into said counterbore and tightening of the threadedly engaged body and coupling members said tube is anchored and supported by compression of said integral boss between said shoulders, and a primary seal is efiected by compressing the tip stresses of said tube adjacent its end face and causing it to fi'ow into pressure tight engagement with said'annular seat.

2. A tube coupling comprising a cylindrical tube, said tube having a squared end face and an integral outwardly struck rounded V-shaped boss spaced a predetermined distance from said end face, a body member having a cylindrical bore corresponding to the internal diameter'of the tube and having a cylindrical counter-bore 'o'oncen'trictherewith of -a diameter to closely'but freely receive the tube end, said body having an outwardly flared shoulder at the outer end of the counterbore to be engaged by the adjacent wall'of said V-s'ha ped'boss and said'body having an annular seat at the juncture of said bore and counter-bore "to be engaged by the squared end face of said tube, said seat being'undercu't on'a reverse bevel and said shoulder and seat being spacedfrom one another by a distance slightly less than the predetermined spacing of said boss andtube end face so that said tube end face engages'with said annular seat prior to the engagement of said boss with said shoulder, and a coupling element embracing said tube and threadedl engaging with said body member, said coupling element having a flared shoulder for engaging the other Wall-of said boss, whereby, on insertion of said tube into said counterboreand tightening 6f the threadedly engaged body "and coupling menibers, said tube is anchored and supported by compression of said integral {boss between said shoulders, and a primary seal is eifecte'd by compressing the tip of said tubeadjacent its end face and causing it to flow into pressure 'tig'ht engagement with said reversely bevele'd annular-seat and the wall of said counterboread jacent 'thereto.

A. 'KINS'EY.

REFERENCES "CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1304314 SchuItis May 12,1931 1, 81'7j854 Sorens'on Aug. 4, 1931 1372,8613 "Wood Aug..23,1 932 2;087,'185 Dillon July -13, 1937 2,0891790 Halpern Aug. 10, 1937 2131509 "G'oepel \et a1 Sept. 27, 1938 "2,251,717 Parker Aug. "5, 1941 '2',414,184 Wurzburger Jan. "14, '1947 FOREIGN PATENTS Number Country Date 3933419 Great Britain June 8, 1933 

